1. Field of the Invention
The present invention relates to an additive used in a plastic molding, to a plastic molding composition, and to a plastic molding. More particularly, the present invention relates to improvements in the coloring of a molding or in coloring aid thereof, or improvements in the dynamic (mechanical) characteristics, or an additive used to provide magnetic properties, a composition for molding and a molded composition.
2. Related Background Art
Hitherto, a black coloring pellet, what is commonly called a "master batch", having a coloring agent such as carbon as a main constituent thereof, has been mainly used for plastic coloring purposes. This coloring pellet is cylindrical or spherical, has a diameter of approximately 2 to 6 mm, and is colorant powder which is melted and kneaded with plastic.
Ordinarily, this coloring pellet is melted and kneaded with a plastic pellet or coarsely ground product by a mixing and kneading apparatus or the like, after which the coloring pellet is formed into a pellet again, or the coloring pellet is mixed with a raw material pellet in a solid state, and directly placed in a molding apparatus. Thus a colored molding is manufactured. In this case, depending upon the kneading performance of the molding apparatus, molding conditions such as molding temperature or molding speed, or the form of a molding, coloring components containing the colorant in the pellet are not dispersed with sufficient uniformity into the plastic. Density irregularities in the molded product and density differences between moldings occur, which phenomena are problematical. In the case of only the colorant, in some cases, colorant particles are separated from plastic with lapse of time and color tone varies, which phenomena are also problematical. In recent years, there has been an increased demand by consumers for more diversified products which satisfies their individual tastes and thus, in particular, in the case of black color there has been a demand for a method of obtaining black color tone different from carbon coloring. In addition, there has been a demand for an additive which can be used to increase the characteristics of a molding according to the application of the molding. Further, there has been a demand for an additive which provides a plastic molding with magnetic properties for specific applications.